Drilling device for large bores



May 22, 1956 A. R. SELIGMAN DRILLING DEVICE FOR LARGE BORES Filed May22. 1952 Tig. 1

Alain R Eeljgman INVENTOR.

ATTORNEY.

United States Patent DRILLING DEVICE FOR LARGE BORES Alain R. Seligman,Houston, Tex.

Application May 22, 1952, Serial No. 289,253

2 Claims. (Cl. 255-19) This invention relates to the production of largediameter bores in the earth and is of particular utility in the sinkingof mine shafts from the surface of the earth to a predetermined level orto a tunnel thcrebeneath.

In the past it has been customary, when sinking mine shafts, ortunnel-to-tunnel shafts, to progressively disintegrate the earthmaterials penetrated along the selected route for the shaft and toperiodically remove loosened material so that the disintegratingoperations may proceed.

The present invention is intended to capitalize upon the advantages,when making large earth bores, of the rotary method of drilling and itis the primary object of the invention to provide an improved method andapparatus utilizing the rotary method of producing large diameter earthbores.

The invention also comprehends, and has for an object, the production ofan earth bore, or shaft, by first providing a pilot hole or bore andthereafter enlarging such bore by steps until a shaft of the desireddiameter is had.

When drilling large bores by the rotary method unusually large weightsupon the drill bit are required in order to produce a satisfactory rateof penetration. Both portable and stationary rotary rigs are incapable,particularly at shallow depths, of exerting sufficient weight upon thebit to effect a satisfactory drilling rate. Also, even if adequateweight could be approximated, buckling of the drill stem would result.It is therefore an additional object of the invention to provide a noveltechnique and apparatus for overcoming these difiiculties.

Still another object is to provide a drilling device which includes apull-down mechanism to apply sufficient force on the drill bit that asatisfactory rate of penetration is obtained.

Another and more specific object of the invention, in one form, is toinitially provide a pilot hole or bore from one level to another leveland to thereafter enlarge such bore by utilizing a reaming bit to whicha downward force is applied by means of a pull-down extending downwardlyinto the pilot bore.

Still another object is to provide, by the rotary method of drilling, apilot bore from one level to a tunnel therebeneath, or between a pointand a tunnel horizontally spaced, pull-down equipment being provided insuch tunnel to exert necessary force upon a drill bit rotatably drivenfrom said level or point, whereby the bore is enlarged to form a shaftto the tunnel.

Other and further objects of the invention will be apparent from thefollowing description and claims, and will be understood by reference tothe accompanying drawing which, by way of illustration, shows apreferred embodiment of the invention.

Fig. 1 is a view partly in section through the earth showing one form ofthe invention and its use in forming a shaft from the earths surface toa tunnel to be served by the shaft.

Fig. 2 is an enlarged View, partly in section, of a rotary drill bitused in accordance with the invention and provided with the pull-downstructure by means of which 2,746,719 Patented May 22, 1956 sufiicientforce axially of the bit may be applied to effectively cut the desiredshaft.

My invention as illustrated in the drawing seeks to provide a shaft 1from the surface 2 of the earth to a lower level shown as the tunnel 3to be served by the shaft. In practicing the invention I first form apilot bore 4 by conventional drilling operations, such operations usingthe drill rig 5 which comprises derrick 6 having crown block 7,travelling block 8 and draw works 9 to control movements of the drillstring 10 to which flushing fluid is supplied by means of the hydraulicswivel 11. The drill stem or string 10 is rotated, as is well known inthe art, by means of the rotary table 12 driven through shaft 13 from asuitable source of power (not shown).

After the pilot bore 4 has been completed an enlarging bit 15 isattached to the drill string 10. A suitable bit, as best seen in Fig. 2,comprises a head 16 which carries roller cutters 17 and 18 havingcutting elements 19 thereon. These cutting elements are so arranged inthe group of cutters that they cut the entire bottom of the shaft formedabout the pilot bore 4 as drilling progresses. It is intended that theoutermost elements 2t? on the cutters will both out and maintain gage ofthe shaft. The cutters 17 and 18 are rotatably mounted on the head 16 inspaced relation with the axis of the bit so that the downward extension25 on the bit head may pass between the innermost ends of the cutters.This extension is enlarged at its lower end and is intended to enter thepilot bore 4 and to serve as a pilot for the bit as it progresses alongthe line determined by the pilot bore.

The head 16 of the enlarging bit 15 may be fabricated in any manner wellknown in the art as for example as shown in U. S. Letters Patent No.959,540. Preferably, as shown in Fig. 2 the head 16 comprisescomplemental bit head segments 21, 22 threaded at their upper ends at 23for attachment to the drill string. These head segments, when assembled,abut on the line 24 as clearly shown in Fig. 2. Each segment has anupper or main portion 24-, upon which one of the cutters is mounted, anda lower portion 25 which forms a portion of the downward extension 25.

The extension or pilot 25 has a circular bore 26 to rotatably receivethe spindle 27 having an enlargement 28 at its upper end within thecavity 29 in the bit head. The enlargement 28 serves as a roller racefor rollers 30 which engage an opposed roller race in the bottom of thecavity 29. A pull-down force is applied to the bit assembly by means ofthe cable 31 secured to the lower end of the spindle as by means of theanchor lug 32.

In practicing the invention the pilot bore 4 is first drilled from thesurface 2 to a point spaced therefrom and shown as the tunnel 3, theline of this bore being the axis of the access shaft to extend from thesurface 2 to the tunnel 3. Drilling of the pilot hole, or bore, may beeffected in the usual manner as relatively small weight upon the bit issufficient to provide the desired rate of penetration when making thissmall diameter bore. As the drill string is rotated by power applied tothe rotary table 12, flushing fluid is pumped through the hydraulicswivel 11 and thence through the drill string and the bit wherebycuttings are removed from the pilot bore as it is formed.

Thereafter the drill bit used in drilling the pilot hole is removed andis replaced by a larger bit of the type shown in Fig. 2 and alreadydescribed. The cable 31 is threaded downwardly through the pilot borewhere it passes beneath the sheave 33, mounted on staging 34 and thenceto the drum 35 within the tunnel 3. Again, the drill stem is rotated bymeans of the rotary table 12. Flushing fluid is forced through thehydraulic swivel 11, the drill string 10 and the bit 15 so that cuttingswill be removed from the enlarged bore or shaft 1 which is being formed.Portions of these cuttings may move both upwardly, through the shaft 1,and downwardly through the pilot bore 4. The latter portion of thecuttings may be received in the tunnel 3 by conveyors or mine cars (notshown) for removal.

While some weight is being applied to the bit 15 by the drill stem whichmay comprise one or more drill collars, additional weight or force uponthe bit is required if a desirable rate of drilling is to be maintained.This additional weight or force is effected by application of tensionupon the cable 31 by driving the drum 35 in the direction indicated bythe arrow 36. it is to be understood that sufiicient power will beavailable that desired torque may be produced upon the drum 35, thateffective cutting action will be had.

inasmuch as large size bits of the type shown at require large weightsfor effective drilling action it may be impractical to provide a desiredsize of shaft 1 through a single enlarging step from the pilot bore 4.Hence, it may be desirable to provide the ultimate diameter of shaft byusing successively larger bits of which each uses the preceding bore asa pilot hole. The invention, therefore, comprehends the production of ashaft 1 by the rotary method of drilling by using a single bit toenlarge from the pilot bore 4 to the desired diameter, or, by using aseries of successively larger hits, the exact number in a particularinstance depending upon the size of the shaft desired, characteristicsof the equipment available and the nature of formations to be penetratedduring the drilling operations.

Obviously the invention is not confined to the precise mechanism forefiecting the pull-down force upon the bit or the precise form of bitshown and described, the only requisite for such mechanism being thatadequate force be applied to the cable 31 to effect desired cuttingaction by the bit.

The invention claimed is:

l. A rotary shaft drilling machine for enlarging to shaft proportions apilot hole drilled between points to be connected by the shaftcomprising in combination, a drill rig including a drill stem and bit tobe rotated thereby and to move axially of and to progressively enlargethe hole, a swivel connection with said drill stem and bit, and meansoperable through said connection for exerting a force axially of thedrill stem and bit to effect disintegrating action of the earthformations about the pilot hole whereby a cylindrical shaft is formedalong the line traversed by the pilot hole.

2. A rotary shaft drilling machine for enlarging to shaft proportions apilot hole drilled between points to be connected by the shaftcomprising in combination, a drill stem, means for rotating said drillstem, a drill bit attached to said drill stem, said drill bit includinga pilot extension adapted to enter and to guide the bit along said pilothole, a swivel connection on said bit, and means attached thereto andextending downwardly into the pilot hole for exerting a pull-down forceupon the bit so that advancement of the bit forms a shaft along the linetraversed by the pilot hole.

References Cited in the file of this patent UNITED STATES PATENTS959,540 Hughes May 31, 1910 1,993,365 Englebright et al. Mar. 5, 19352,035,888 Howard Mar, 31, 1936 2,058,628 Reed Oct. 27, 1936 2,074,003Templeton et al Mar. 16, 1937 2,281,614 Ogran May 5, 1942 2,349,033Elliott May 16, 1944 2,664,273 Merrick Dec. 29, 1953 2,684,834 Miller etal. July 27, 1954 FOREIGN PATENTS 427,535 Germany Apr. 9, 1926

